1. Field of the Invention
The present invention relates to a method and apparatus for estimating the fundamental frequency, that is, the pitch, of a speech signal, and more particularly to a method and an apparatus by which mixture Gaussian distributions are generated based on candidate pitches having high period estimating values, a mixture Gaussian distribution having a high likelihood is selected and dynamic programming is executed so that the pitch of the speech signal can be accurately estimated.
2. Description of Related Art
Recently, various applications for recognizing, synthesizing and compressing a speech signal have been developed. In order to accurately recognize, synthesize and compress a speech signal, it is very important to estimate the fundamental frequency, that is, the pitch, of the speech signal, and, accordingly, many studies on a method for accurately estimating the pitch have been conducted. General methods for extracting the pitch include a method for extracting the pitch from a time domain, a method for extracting the pitch from a frequency domain, a method for extracting the pitch from an autocorrelation function domain and a method for extracting the pitch from the property of a waveform.
U.S. Pat. No. 6,012,023 discloses a method for extracting voiced sound and voiceless sound of a speech signal to accurately detect the pitch of the speech signal which has an autocorrelation value with a halving or doubling pitch that is higher than the pitch to be extracted.
U.S. Pat. No. 6,035,271 discloses a method for selecting candidate pitches from a normalized autocorrelation function, determining the points of anchor pitches based on the selected candidate pitches, and forwardly and backwardly performing a search from the points of the anchor pitches to extract the pitch.
However, these conventional pitch extracting methods are affected by a Formant frequency, and thus, the pitch cannot be accurately estimated.